Gapfill of variable aspect ratio features with a composite PEALD and PECVD method

ABSTRACT

Provided herein are methods and apparatus for filling one or more gaps on a semiconductor substrate. The disclosed embodiments are especially useful for forming seam-free, void-free fill in both narrow and wide features. The methods may be performed without any intervening etching operations to achieve a single step deposition. In various implementations, a first operation is performed using a novel PEALD fill mechanism to fill narrow gaps and line wide gaps. A second operation may be performed using PECVD methods to continue filling the wide gaps.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority to U.S.application Ser. No. 14/987,542, filed Jan. 4, 2016, titled “GAPFILL OFVARIABLE ASPECT RATIO FEATURES WITH A COMPOSITE PEALD AND PECVD METHOD,”which is a continuation of U.S. application Ser. No. 14/137,860 (issuedas U.S. Pat. No. 9,257,274), filed Dec. 20, 2013, titled “GAPFILL OFVARIABLE ASPECT RATIO FEATURES WITH A COMPOSITE PEALD AND PECVD METHOD,”which claims the benefit of U.S. Provisional Application No. 61/884,923,filed Sep. 30, 2013, titled “GAPFILL OF VARIABLE ASPECT RATIO FEATURESWITH A COMPOSITE PEALD AND PECVD METHOD,” all of which are incorporatedherein by reference in their entireties and for all purposes. U.S.application Ser. No. 14/137,860 is also a continuation-in-part of U.S.patent application Ser. No. 13/084,399 (issued as U.S. Pat. No.8,728,956), filed Apr. 11, 2011, and titled “PLASMA ACTIVATED CONFORMALFILM DEPOSITION,” which claims benefit of the following prior U.S.Provisional Application Nos. 61/324,710, filed Apr. 15, 2010, and titled“PLASMA ACTIVATED CONFORMAL FILM DEPOSITION”; 61/372,367, filed Aug. 10,2010, and titled “PLASMA ACTIVATED CONFORMAL FILM DEPOSITION”;61/379,081, filed Sep. 1, 2010, and titled “PLASMA ACTIVATED CONFORMALFILM DEPOSITION”; and 61/417,807, filed Nov. 29, 2010, and titled“PLASMA ACTIVATED CONFORMAL FILM DEPOSITION,” all of which are hereinincorporated by reference in their entireties and for all purposes.

BACKGROUND

The fabrication of integrated circuits includes many diverse processingsteps. One of the operations frequently employed is the deposition of adielectric film into a gap between features patterned over or intosilicon substrates. One of the goals in depositing such material is toform a void-free, seam-free fill in the gap. As device dimensions becomesmaller in the context of DRAM, flash memory and logic, for example, ithas become increasingly difficult to achieve this type of ideal fill.

While deposition methods such as high density plasma (HDP),sub-atmospheric chemical vapor deposition (SACVD), and low pressurechemical vapor deposition (LPCVD) have been used for gap fill, thesemethods do not achieve the desired fill capability. Flowable chemicalvapor deposition and spin-on dielectric (SOD) methods can achieve thedesired fill, but tend to deposit highly porous films. Further, thesemethods are especially complex and costly to integrate, as they requiremany extra processing steps. Atomic layer deposition (ALD) processeshave also been used for gap fill, but these processes suffer from longprocessing times and low throughput, especially for large gaps. In somecases, multi-step deposition processes are used, includingdeposition-etch-deposition processes which require distinct etchingoperations between subsequent deposition operations. The etching may bedone to remedy or prevent void formation in the gap. While this methodis useful, it would be preferable to use a process that involves onlydeposition, with no required etch operations.

A further challenge is simultaneously filling gaps of different sizes ona substrate. For example, a deposition method optimized for a wide gapwith a small aspect ratio may not be suitable for filling a narrow gapwith a large aspect ratio, and vice versa. Therefore, a method ofachieving void-free, seam-free fill of dielectric material into a gap isneeded, particularly one that may be used to simultaneously fill gaps ofvarious sizes.

SUMMARY

Certain embodiments herein relate to methods and apparatus for filling agap on a semiconductor substrate. In certain cases, the gap is filledthrough a plasma enhanced atomic layer deposition (PEALD) operation. Inother cases, the gap is filled through a hybrid method including bothPEALD and plasma enhanced chemical vapor deposition (PECVD) operations.In one aspect of the embodiments herein, a method is provided forfilling a gap including (a) introducing a first reactant in vapor phaseinto a reaction chamber having the substrate therein, and allowing thefirst reactant to adsorb onto the substrate surface; (b) introducing asecond reactant in vapor phase into the reaction chamber and allowingthe second reactant to adsorb onto the substrate surface; (c) exposingthe substrate surface to plasma to drive a surface reaction between thefirst and second reactants on the substrate surface to form a film layerthat lines the bottom and sidewalls of the gap; (d) sweeping thereaction chamber without performing a pumpdown; and (e) repeatingoperations (a) through (d) to form additional film layers, where whenopposing film layers on opposite sidewalls of the gap approach oneanother, surface groups present on the opposing film layers crosslinkwith one another to thereby fill the gap. The methods may be used tofill the gap without the formation of a void or seam.

In some embodiments, the first reactant is a silicon-containing reactantand the second reactant is an oxidizing reactant. For example, the firstreactant may include bis(tertiary-butyl-amino)silane (BTBAS). In afurther example, the second reactant may include oxygen and/or nitrousoxide. In various cases, the gap is reentrant. Further, in manyembodiments, the gap is filled through a mechanism that may becharacterized at least in part as a bottom-up fill mechanism. Thisbottom-up fill mechanism may achieve a seam-free, void-free fill, evenwhere a gap is reentrant.

In another aspect of the disclosed embodiments, a method of filling agap on a substrate surface is provided, including (a) introducing afirst reactant in vapor phase into a reaction chamber having thesubstrate therein, and allowing the first reactant to adsorb onto thesubstrate surface; (b) introducing a second reactant in vapor phase intothe reaction chamber and allowing the second reactant to adsorb onto thesubstrate surface; and (c) exposing the substrate surface to plasma todrive a surface reaction between the first and second reactants on thesubstrate surface to form a film layer that lines the bottom andsidewalls of the gap, where the film is denser and/or thinner near thefield region and upper sidewalls of the gap compared to near the bottomand lower sidewalls of the gap. The method may include an operation of(d) sweeping the reaction chamber without performing a pumpdown after(c) is performed. In some embodiments, the method includes repeatingoperations (a) through (c) (or (a) through (d)) to form additional filmlayers to thereby fill the gap. In certain embodiments the gap may befilled through a bottom-up fill mechanism, without the formation of avoid or seam.

In another aspect of the disclosed embodiments, a method of filling agap on a substrate surface is provided, including (a) introducing afirst reactant in vapor phase into a reaction chamber having thesubstrate therein, and allowing the first reactant to adsorb onto thesubstrate surface; (b) introducing a second reactant in vapor phase intothe reaction chamber and allowing the second reactant to adsorb onto thesubstrate surface; (c) exposing the substrate surface to plasma to drivea surface reaction between the first and second reactants on thesubstrate surface to form a film layer that lines the bottom andsidewalls of the gap, (d) sweeping the reaction chamber withoutperforming a pumpdown; and repeating operations (a) through (d) to formadditional film layers where ligands of one or more reactants arepreferentially buried in the film near the bottom and lower sidewalls ofthe gap compared to the field region and upper sidewalls of the gap. Themethod may include an operation of (d) sweeping the reaction chamberwithout performing a pumpdown after (c) is performed. In certainembodiments, the gap may be filled through a bottom-up fill mechanismwithout the formation of a void or seam.

In a further aspect of the disclosed embodiments, a method of filling agap on a substrate surface is provided, including (a) introducing afirst reactant in vapor phase into a reaction chamber having thesubstrate therein, and allowing the first reactant to adsorb onto thesubstrate surface; (b) introducing a second reactant in vapor phase intothe reaction chamber and allowing the second reactant to adsorb onto thesubstrate surface; (c) exposing the substrate surface to plasma to drivea surface reaction between the first and second reactants on thesubstrate surface to form a film lining the gap; (d) sweeping or purgingthe reaction chamber; (e) introducing a third reactant in vapor phaseand fourth reactant in vapor phase into the reaction chamberconcurrently; and (f) generating a plasma from the vapor phase reactantsto drive a gas phase reaction between the third and fourth reactants,where the gas phase reaction produces a gap-filling material, and wherethe gap-filling material partially or completely fills the gap on thesubstrate surface.

The first and second reactants may be the same as at least one of thethird and fourth reactants. For example, the first and second reactantsmay each be the same as the third and fourth reactants. In other cases,there may be no overlap between the first and second reactants and thethird and fourth reactants. In many cases, the film formed in (c) is thesame material as the gap-filling material formed in (f). For example,the film formed in (c) and the gap-filling material formed in (f) may besilicon oxide. In these cases, the first reactant may be asilicon-containing reactant and the second reactant may be an oxidizingreactant. For example, the first reactant may include BTBAS. In afurther example, the second reactant may include oxygen and/or nitrousoxide. In these or other cases, examples of the third reactant may beTEOS or silane, with examples of the fourth reactant being an oxidizingreactant.

In some implementations, operations (a) through (c) are repeated beforeoperations (e) through (f), and no pumpdown occurs after each iterationof operation (c). In these or other cases, the method may be performedwithout any intervening etching operations. One advantage of thedisclosed embodiments is that the method may be performed in a singlereaction chamber. In many cases, the substrate is not removed from thereaction chamber during or between any of operations (a) through (f). Insome implementations, operations (a) through (c) include forming aconformal film that is thicker at the bottom of the gap than on theupper sidewalls of the gap. This may be achieved in a variety of ways.In some embodiments, operation (c) may include preferentially densifyingthe film near the top of the gap compared to the film near the bottom ofthe gap. In these or other embodiments, operation (c) may includepreferentially burying ligands of one or more reactants in the film nearthe bottom of the gap compared to near the upper sidewalls of the gap.Operation (c) may also include promoting crosslinking between the filmformed on a first sidewall of the gap and the film formed on an opposingsidewall of the gap.

In yet another aspect of the disclosed embodiments, a method of fillinggaps on a substrate surface is provided, including (a) introducing afirst reactant in vapor phase into a reaction chamber having thesubstrate therein, and allowing the first reactant to adsorb onto thesubstrate surface, where the substrate has at least a narrow gap havinga critical dimension less than about 50 nm and a wide gap having acritical dimension greater than or equal to about 50 nm; (b) introducinga second reactant in vapor phase into the reaction chamber and allowingthe second reactant to adsorb onto the substrate surface; (c) exposingthe substrate surface to plasma to drive a surface reaction between thefirst and second reactants on the substrate surface to form a film,where the film completely fills the narrow gap and lines the wide gap;(d) sweeping or purging the reaction chamber; (e) introducing a thirdreactant in vapor phase and fourth reactant in vapor phase into thereaction chamber concurrently; and (f) generating a plasma from thevapor phase reactants to drive a gas phase reaction between the thirdand fourth reactants, where the gas phase reaction produces agap-filling material, and wherein the gap-filling material partially orcompletely fills the wide gap on the substrate surface.

In some cases, the narrow gap has an aspect ratio of greater than about4:1 and the wide gap has an aspect ratio of less than or equal to about4:1. The narrow gap may be reentrant in some embodiments. Even where thenarrow gap is reentrant, it may be filled without forming seams orvoids. In some implementations, operations (a) through (c) are repeatedbefore operations (e) through (f), and no pumpdown occurs after eachiteration of operation (c). In these or other cases, the film formed in(c) may be the same material as the gap-filling material formed in (f).In many embodiments, the method is performed without any interveningetching operations. The disclosed embodiments allow the narrow gap andwide gap to be filled without forming seams or voids.

In a further aspect of the disclosed embodiments, an apparatus forfilling gaps on a semiconductor substrate is disclosed. The apparatusmay include a reaction chamber, a substrate supporter, a plasmageneration source, one or more process gas inlets, one or more outlets,and a controller. The controller may be configured to perform any of themethods disclosed herein.

Another aspect of the disclosed embodiments is a method of filling oneor more gaps on a semiconductor substrate with a dielectric material,including: (a) depositing a silicon-containing film in the one or moregaps on the substrate through a plasma enhanced atomic layer depositionsurface reaction to partially fill the one or more gaps with thesilicon-containing film; and (b) depositing additionalsilicon-containing film on the film deposited in (a) through a plasmaenhanced chemical vapor deposition gas-phase reaction to complete fillof the one or more gaps with the silicon-containing film.

These and other features will be described below with reference to theassociated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flowchart of a method of depositing a film through aplasma enhanced atomic layer deposition (PEALD) process.

FIG. 2 shows a substrate having gaps of different aspect ratios that maybe filled according to the disclosed embodiments.

FIG. 3 shows the substrate of FIG. 2 after a PEALD deposition process isperformed.

FIG. 4 shows a close-up view of a narrow gap of FIGS. 2 and 3 as thePEALD process is performed to fill the gap.

FIG. 5 shows a flowchart of a method of depositing a film through aplasma enhanced chemical vapor deposition (PECVD) process.

FIG. 6 shows a block diagram of an apparatus that may be used to carryout the disclosed methods.

FIG. 7 depicts a multi-station apparatus that may be used to carry outthe disclosed methods.

FIG. 8 shows a partially filled high aspect ratio gap that was filledaccording to the disclosed PEALD methods.

FIGS. 9-11 show additional pictures of high aspect ratio gaps filledaccording to the disclosed PEALD methods.

FIG. 12 shows a wide gap filled with silicon oxide deposited accordingto a disclosed PECVD method.

DETAILED DESCRIPTION

In this application, the terms “semiconductor wafer,” “wafer,”“substrate,” “wafer substrate,” and “partially fabricated integratedcircuit” are used interchangeably. One of ordinary skill in the artwould understand that the term “partially fabricated integrated circuit”can refer to a silicon wafer during any of many stages of integratedcircuit fabrication thereon. A wafer or substrate used in thesemiconductor device industry may have a diameter of 200 mm, or 300 mm,or 450 mm. The following detailed description assumes the invention isimplemented on a wafer. However, the invention is not so limited. Thework piece may be of various shapes, sizes, and materials. In additionto semiconductor wafers, other work pieces that may take advantage ofthis invention include various articles such as printed circuit boards,glass panels, and the like.

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the presented embodiments.The disclosed embodiments may be practiced without some or all of thesespecific details. In other instances, well-known process operations havenot been described in detail to not unnecessarily obscure the disclosedembodiments. While the disclosed embodiments will be described inconjunction with the specific embodiments, it will be understood that itis not intended to limit the disclosed embodiments.

Conventional gap fill techniques have been unsuccessful in achievingvoid-free, seam-free fill for high density films in high aspect ratiogaps. HDP, SACVD and LPCVD have only limited fill capability, andtypically result in the formation of voids and seams. These voids andseams can open up after a chemical mechanical polishing (CMP) operation,or after an etch-back is performed. These opened seams and voids canthen trap materials, such as polysilicon and tungsten, that aresubsequently deposited. These materials are often incompletely removedin subsequent CMP or etch-back operations, and can remain in the deviceto cause shorts and/or loss of yield. Flowable CVD (e.g., flowableoxide) and SOD techniques have complex integration schemes that mayresult in high costs associated with the various additional stepsinvolved.

Certain embodiments herein relate to a hybrid method of fillingdifferently sized gaps on a semiconductor substrate. The first portionof the method relates to an ALD operation, for example a plasma enhancedALD (PEALD) operation. The ALD operation may be performed in a novel wayto promote a bottom-up type fill in narrow gaps. This bottom-up fillmechanism helps achieve the void-free, seam-free fill, particularly innarrow gaps (e.g., gaps having a critical dimension (CD) of about 50 nmor less) and/or gaps having high aspect ratios (e.g., depth to widthaspect ratio of about 4:1 or higher). The ALD operation also acts toform a layer on, but not completely fill, wider gaps present on thesubstrate (e.g., gaps having a CD larger than about 50 nm) having loweraspect ratios (e.g., aspect ratios of about 4:1 or lower).

The second portion of the method relates to a plasma enhanced chemicalvapor deposition (PECVD) method that is used to fill the remainder ofthe wider gaps. In certain embodiments, this method may be performedusing a direct (in situ) capacitively coupled plasma. In manyembodiments, a radio frequency (RF) plasma source is employed, thoughany type of plasma source capable of generating a direct plasma may beemployed, including microwave and DC sources. Further, in someembodiments, a remotely-generated plasma may be employed. The remoteplasma may be capacitively-coupled or inductively-coupled according tovarious embodiments.

The plasmas used in the PECVD methods described herein may have lowerplasma density than high density plasmas generated by in-situinductively coupled plasma generators such as those used in HDPprocesses. For example, in HDP processes plasma densities may be on theorder of about 10¹¹-10¹³ ions/cm³, as opposed to about 10⁸-10¹⁰ ions/cm³for PECVD processes in certain embodiments. HDP methods generally do notproduce the required fill results, as described above, and typicallyrequire the use of etch operations between subsequent deposition steps.In HDP methods, charged dielectric precursor species are directeddownwards to fill the gap. This results in some sputtering of material,which can then redeposit on the sidewalls of the gap, especially nearthe top of the gap, as well as in the field region. Further, unchargedparticles present in the chamber may deposit in the upper sidewallregion, as well. This unwanted deposition can build up to form sidewalldeposits and top-hats, which prevent the gap from being uniformlyfilled. Etch steps may be used to combat the undesired upper sidewalldeposition that occurs with HDP, though this increases the complexity ofthe deposition method. If no etch steps are performed, the gap willgenerally not be able to fill without formation of a void. The HDPmethods are also much more expensive to implement, with a lowerthroughput than PECVD methods.

According to various embodiments, the PEALD and PECVD methods may beimplemented in the same chamber. Both of these types of processes run insimilar pressure and flow regimes, and can use the same RF powersources. Further, the PECVD methods may be performed in a single step,meaning that no intervening etching operations (or other processes suchas deposition processes) are required. By contrast, it is not practicalto run PEALD and HDP processes in the same chamber. First, the twoprocesses operate in substantially different pressure regimes. PEALDprocesses generally run in the range of a few Torr, and benefit fromhigh gas flows for purging. HDP processes operate in the mTorr range,which requires relatively low gas flows compared to what is used withPEALD. Next, HDP processes are typically practiced in large volumechambers, while ALD processes benefit from substantially smallervolumes. Furthermore, HDP processes generally require a different powersource than PEALD, which would further complicate reactor design.

Although HDP processes have shown good gap fill, HDP processes sufferfrom engineering problems related to “forbidden gap” sizes. Where ahybrid ALD/HDP deposition approach is used, a forbidden gap may existwhere the CD of the gap is slightly larger than 2× the thickness of theALD layer deposited. In these cases, the HDP processes are unable tofill the remaining gap. The PECVD methods described herein can fill gapsincluding those previously lined with PEALD. After any challengingstructures are lined/filled with PEALD, the PECVD process may be used tofill remaining structures in a less conformal manner.

The PECVD operation is advantageous in achieving a high deposition rateto fill larger gaps that would take a long time to fill through ALDalone. In some embodiments, however, the methods include only the firstoperation of performing PEALD.

In various embodiments, the PEALD and PECVD operations are performed inthe same chamber. This setup is beneficial, as there is no need totransfer the substrate from a PEALD reaction chamber to a PECVD reactionchamber. Thus, there is no need to worry about moisture getting on orinto the film, and there is no corresponding need to perform ade-gassing operation or high temperature anneal to remove the moisturebefore performing the PECVD operation. Another benefit to the singlechamber approach is that it reduces capital costs, cycle times andprocess flow complexity.

Variations may be made to the basic method described above to achievedifferent hybrid filling scenarios. In one example, a first portion ofthe method includes a PEALD operation performed under optimum conditionsfor filling a high aspect ratio gap, and a second portion of the methodincludes a more relaxed PEALD operation such as one having reduced doseand purge times. These relaxed PEALD operations may also promote PECVDor partial PECVD deposition. In another example, an etch step is used totaper the gap profile. The etch step may be performed between a firstportion of the method and a second portion of the method (e.g., betweena PEALD operation and a PECVD operation), or within a single portion ofthe method (e.g., between two PEALD operations or between two PECVDoperations). Of course, the methods may be combined as appropriate. Theoptimum solution will depend on the actual distribution of aspect ratiosand gap dimensions present on the substrate.

Combined PEALD and PECVD methods for filling gaps on substrates arediscussed in U.S. patent application Ser. No. 13/084,399, which wasincorporated by reference above. In certain cases, as discussed in Ser.No. 13/084,399, there may be a transition phase between an PEALDoperation and a PECVD operation in which both PEALD surface reactionsand PECVD gas phase reactions occur simultaneously.

In such embodiments, the completed film is generated in part by ALD/CFDand in part by a CVD process such as PECVD. Typically, the ALD/CFDportion of the deposition process is performed first and the PECVDportion is performed second, although this need not be the case. MixedALD/CFD with CVD processes can improve the step coverage over that seenwith CVD alone and additionally improve the deposition rate over thatseen with ALD/CFD alone. In some cases, plasma or other activation isapplied while one ALD/CFD reactant is flowing in order to produceparasitic CVD operations and thereby achieve higher deposition rates, adifferent class of films, etc.

In certain embodiments, two or more ALD/CFD phases may be employedand/or two or more CVD phases may be employed. For example, an initialportion of the film may be deposited by ALD/CFD, followed by anintermediate portion of the film being deposited by CVD, and a finalportion of the film deposited by ALD/CFD. In such embodiments, it may bedesirable to modify the CVD portion of the film, as by plasma treatmentor etching, prior to depositing the later portion of the film byALD/CFD.

A transition phase may be employed between the ALD/CFD and CVD phases.The conditions employed during such transition phase different fromthose employed in either the ALD/CFD or the CVD phases. Typically,though not necessarily, the conditions permit simultaneous ALD/CFDsurface reactions and CVD type gas phase reactions. The transition phasetypically involves exposure to a plasma, which may be pulsed forexample. Further, the transition phase may involve delivery of one ormore reactants at a low flow rate, i.e., a rate that is significantlylower than that employed in the corresponding ALD/CFD phase of theprocess.

Methods Plasma Enhanced Atomic Layer Deposition

The disclosed PEALD processes are useful in achieving void-free,seam-free fill of relatively narrow/high aspect ratio features.Unexpectedly, certain embodiments of the processes appear to result in abottom-up fill mechanism where material is preferentially deposited nearthe bottom of the gap as opposed to the top of the gap as the gap isbeing filled. Although deposition happens on the sidewalls and fieldregion as well, the film deposits thicker at/near the bottom of the gapand in many cases achieves a tapered profile as the gap is filled. Thetapered profile is defined to mean that the film deposits thicker nearthe bottom and thinner near the top of the gap, as shown in theExperimental section, below. This tapered profile is especially usefulin achieving a high quality fill without voids or seams in high aspectratio features. This fill mechanism was unexpected, as atomic layerdeposition methods typically result in the formation of a seam as thesidewalls close in towards one another. By promoting bottom-up fill,this seam can be avoided and a more robust device results.

Without wishing to be bound by any theory or mechanism of action, it isbelieved that the bottom-up fill mechanism may be caused by preferentialfilm densification near the top of the gap. As the film is exposed toplasma, species present in the plasma (especially ions) bombard the filmsurface, thereby compacting and densifying the film. Under appropriateconditions, this densification may happen preferentially near the top ofthe gap. Due to the shape of the gap, it is much easier for ions tobombard the film in the field region and near the top of the gap, asopposed to near the bottom of the gap, which is much more protected.Thus, the film near the top becomes denser and thinner than the materialnear the bottom of the trench, which remains thicker and less dense.

Another factor that may promote seam-free, void-free, bottom-up fillingis that crosslinking may occur between groups present on opposingsidewalls of the gap. As deposition proceeds and the sidewalls close intowards one another, the terminal groups may crosslink with one another,thus avoiding any seam. In the case of a gap-filling silicon oxide film,for example, surface hydroxyls/silanols on one sidewall may crosslinkwith surface hydroxyls/silanols on the opposing wall, thereby liberatingwater and forming a silicon-oxide matrix. These terminal cross-linkinggroups may preferentially be found on the sidewalls of a gap.

A further factor that may promote seam-free, void-free, bottom-upfilling is that ligand byproducts may be liberated from the film in anon-uniform manner, such that the byproducts become preferentiallytrapped at or near the bottom of the gap as opposed to near the top ofthe gap. This entrapment may lead to a higher deposition rate within thefeature, especially near the bottom of the gap. For example, wherebis(tertiary-butyl-amino)silane (BTBAS) is used as a precursor, one typeof ligand byproduct that may become entrapped is tert-butylamine (TBA).It is understood, however, that where ligands become trapped in agrowing film, the properties of the film may be affected to some degree.

FIG. 1 presents a flowchart for a method of performing a plasma enhancedatomic layer deposition process 100. The process 100 begins at operation101, where a dose of a first reactant is provided to a reaction chambercontaining a substrate. The substrate will typically have gaps thereinthat are to be filled, partially or completely, through the PEALDprocess. In one embodiment, the PEALD process 100 completely fills gapsof a first type, and partially fills (e.g., lines) gaps of a secondtype, as discussed further below. In various cases, the first reactantmay be a silicon-containing reactant. Next, at operation 103 thereaction chamber is purged, for example with an inert gas or a nitrogencarrier gas. This helps remove any remaining first reactant from thereaction chamber.

At operation 105, the second reactant is provided to the reactionchamber. In certain cases, the second reactant is an oxidizing reactant.The second reactant may also be a mix of reactants. In a particularembodiment, the second reactant is a roughly equal volume flow of oxygenand nitrous oxide. As used herein, the phrase “roughly equal volumeflow” means that the flow of a first species and the flow of a secondspecies do not differ by more than about 20%, as measured in SLM. Thesecond reactant is provided in operation 105, which may includepre-flowing the reactant before flowing the reactant coincident withplasma activation in operation 107. When the plasma is activated, itdrives a reaction between the first and second reactants on the surfaceof the substrate. Next, the plasma is extinguished, and then thereaction chamber is purged, for example with inert gas or a nitrogencarrier gas. This operation 109 is referred to as the post-RF purge.

The method 100 is typically repeated a number of times to build up thedesired film thickness. By using the conditions and methods disclosedherein, the method 100 can result in a fill having a tapered profile andbottom-up fill characteristics. These factors promote void-free,seam-free fill. Advantageously, the film deposited through the disclosedmethods are fairly dense.

In a particular example, operation 101 includes providing BTBAS (orother primary reactant) at a flow rate of about 0.5-2.5 mL/min, or about1.5-2.5 L/min, for example 2 mL/min, for a time period of between about0.1-1 second, or about 0.2-0.5 seconds, for example about 0.3 seconds.Operation 103 includes purging the reaction chamber with inert gas forbetween about 0.1-1 seconds, or between about 0.2-0.5 seconds, forexample about 0.3 seconds. Operation 105 includes co-flowing O₂ and N₂Oat a flow rate between about 2-20 SLM each, or between about 8-12 SLMeach, for example about 10 SLM each. Coincident with this reactantdelivery, a plasma is generated at operation 107 using between about 300W-10 kW, or between about 4-6 kW, for example about 5 kW RF power. Thesevalues represent the total RF power delivered, which is divided amongfour stations/pedestals. The plasma exposure lasts for a durationbetween about 10 milliseconds and 3 seconds, or between about 0.25-1second, for example about 0.5 seconds. The RF frequency applied togenerate the plasma may be about 13.56 or 27 MHz. Next, the reactionchamber is purged with inert gas at operation 109 for a time periodbetween about 10 milliseconds and 5 seconds, or between about 50-150milliseconds, for example about 90 milliseconds. It should be understoodthat the above conditions are examples, with other reactants, flowrates, pulse times, and power used as appropriate for the particularimplementation.

The PEALD methods described herein may be conformal film deposition(CFD) methods. Plasma enhanced conformal film deposition techniques andapparatus are further discussed and described in U.S. patent applicationSer. No. 13/084,399, filed Apr. 11, 2011, and titled “PLASMA ACTIVATEDCONFORMAL FILM DEPOSITION,” which is incorporated by reference in itsentirety above.

PEALD Reactants

The disclosed methods and apparatus are not limited to use withparticular precursors. While the methods have already proven to beeffective with certain precursors (as shown in the Experimental section)it is believed that the methods may also be used with a variety of otherprecursors to gain similar benefits.

At least one of the reactants will generally contain an element that issolid at room temperature, the element being incorporated into the filmformed by the PEALD/PECVD method. This reactant may be referred to as aprincipal reactant. The principal reactant typically includes, forexample, a metal (e.g., aluminum, titanium, etc.), a semiconductor(e.g., silicon, germanium, etc.), and/or a non-metal or metalloid (e.g.,boron). The other reactant is sometimes referred to as an auxiliaryreactant or a co-reactant. Non-limiting examples of co-reactants includeoxygen, ozone, hydrogen, hydrazine, water, carbon monoxide, nitrousoxide, ammonia, alkyl amines, and the like. The co-reactant may also bea mix of reactants, as mentioned above.

The PEALD/PECVD process may be used to deposit a wide variety of filmtypes and in particular implementations to fill gaps with these filmtypes. While much of the discussion herein focuses on the formation ofundoped silicon oxides, other film types such as nitrides, carbides,oxynitrides, carbon-doped oxides, nitrogen-doped oxides, borides, etc.may also be formed. Oxides include a wide range of materials includingundoped silicate glass (USG), doped silicate glass. Examples of dopedglasses included boron doped silicate glass (BSG), phosphorus dopedsilicate glass (PSG), and boron phosphorus doped silicate glass (BPSG).Still further, the PEALD/PECVD process may be used for metal depositionand feature fill.

While the disclosed embodiments are not limited to particular reactants,an exemplary list of reactants is provided below.

In certain embodiments, the deposited film is a silicon-containing film.In these cases, the silicon-containing reactant may be for example, asilane, a halosilane or an aminosilane. A silane contains hydrogenand/or carbon groups, but does not contain a halogen. Examples ofsilanes are silane (SiH₄), disilane (Si₂H₆), and organo silanes such asmethylsilane, ethylsilane, isopropylsilane, t-butylsilane,dimethylsilane, diethylsilane, di-t-butyl silane, allylsilane, sec-butylsilane, thexylsilane, isoamylsilane, t-butyldisilane,di-t-butyldisilane, tetra-ethyl-ortho-silicate (also known astetra-ethoxy-silane or TEOS) and the like. A halosilane contains atleast one halogen group and may or may not contain hydrogens and/orcarbon groups. Examples of halosilanes are iodosilanes, bromosilanes,chlorosilanes and fluorosilanes. Although halosilanes, particularlyfluorosilanes, may form reactive halide species that can etch siliconmaterials, in certain embodiments described herein, thesilicon-containing reactant is not present when a plasma is struck.Specific chlorosilanes are tetrachlorosilane (SiCl₄), trichlorosilane(HSiCl₃), dichlorosilane (H₂SiCl₂), monochlorosilane (ClSiH₃),chloroallylsilane, chloromethylsilane, dichloromethyl silane,chlorodimethylsilane, chloroethylsilane, t-butylchlorosilane,di-t-butylchlorosilane, chloroisopropylsilane, chloro-sec-butylsilane,t-butyldimethylchlorosilane, thexyldimethylchlorosilane, and the like.An aminosilane includes at least one nitrogen atom bonded to a siliconatom, but may also contain hydrogens, oxygens, halogens and carbons.Examples of aminosilanes are mono-, di-, tri- and tetra-aminosilane(H₃Si(NH₂)₄, H₂Si(NH₂)₂, HSi(NH₂)₃ and Si(NH₂)₄, respectively), as wellas substituted mono-, di-, tri- and tetra-aminosilanes, for example,t-butylaminosilane, methylaminosilane, tert-butylsilanamine,bis(tertiarybutylamino)silane (SiH₂(NHC(CH₃)₃)₂ (BTBAS), tert-butylsilylcarbamate, SiH(CH₃)—(N(CH₃)₂)₂, SiHCl—(N(CH₃)₂)₂, (Si(CH₃)₂NH)₃ andthe like. A further example of an aminosilane is trisilylamine(N(SiH₃)).

In other cases, the deposited film contains metal. Examples ofmetal-containing films that may be formed include oxides and nitrides ofaluminum, titanium, hafnium, tantalum, tungsten, manganese, magnesium,strontium, etc., as well as elemental metal films. Example precursorsmay include metal alkylamines, metal alkoxides, metal alkylamides, metalhalides, metal ß-diketonates, metal carbonyls, organometallics, etc.Appropriate metal-containing precursors will include the metal that isdesired to be incorporated into the film. For example, atantalum-containing layer may be deposited by reactingpentakis(dimethylamido)tantalum with ammonia or another reducing agent.Further examples of metal-containing precursors that may be employedinclude trimethylaluminum, tetraethoxytitanium, tetrakis-dimethyl-amidotitanium, hafnium tetrakis(ethylmethylamide),bis(cyclopentadienyl)manganese, bis(n-propyl cyclopentadienyl)magnesium,etc.

In certain implementations, an oxygen-containing oxidizing reactant isused. Examples of oxygen-containing oxidizing reactants include oxygen,ozone, nitrous oxide, carbon monoxide, etc.

In some embodiments, the deposited film contains nitrogen, and anitrogen-containing reactant is used. A nitrogen-containing reactantcontains at least one nitrogen, for example, ammonia, hydrazine, amines(e.g., amines bearing carbon) such as methylamine, dimethylamine,ethylamine, isopropylamine, t-butylamine, di-t-butylamine,cyclopropylamine, sec-butylamine, cyclobutylamine, isoamylamine,2-methylbutan-2-amine, trimethylamine, diisopropylamine,diethylisopropylamine, di-t-butylhydrazine, as well as aromaticcontaining amines such as anilines, pyridines, and benzylamines. Aminesmay be primary, secondary, tertiary or quaternary (for example,tetraalkylammonium compounds). A nitrogen-containing reactant cancontain heteroatoms other than nitrogen, for example, hydroxylamine,t-butyloxycarbonyl amine and N-t-butyl hydroxylamine arenitrogen-containing reactants.

Other precursors, such as will be apparent to or readily discernible bythose skilled in the art given the teachings provided herein, may alsobe used.

Gap Conditions

The disclosed PEALD process is especially useful for filling relativelynarrow gaps (CD< about 50 nm) having a relatively high aspect ratio (AR>about 4:1). However, the process may also be performed on larger gapsand gaps having smaller ARs, as well.

In various embodiments, the PEALD process is performed on a substratehaving at least two different types of gaps. A first type may includegaps having a CD less than about 50 nm, and/or an AR greater than about4:1. This first type is referred to as a narrow gap. A second type mayinclude gaps having a CD greater than about 50 nm, and/or an AR lessthan about 4:1. This second type is referred to as a wide gap. For thereasons discussed above, it can be difficult to simultaneously fill bothnarrow and wide gaps. Another way to characterize the different types ofgaps is by comparing their sizes relative to one another. In some cases,a wide gap is at least about 2 times, or at least about 5 times, or atleast about 10 times wider than a narrow gap. In these or other cases,the AR of the narrow gap may be at least about 2 times, or at leastabout 5 times, or at least about 10 times greater than the AR of thewide gap.

In many implementations where the PEALD process is performed on asubstrate having both narrow and wide gaps, the PEALD process will actto completely fill the narrow gap, and line the surface of the wide gap.FIG. 2 presents a substrate 200 having two different types of gaps 202and 204. The aspect ratio of the gaps is calculated as the height of thegap divided by the width of the gap. These dimensions are labeled inFIG. 2. Gaps 202 are narrow gaps having an aspect ratio slightly largerthan 4:1. Gaps 204 are wide gaps having an aspect ratio of about 1:2.

FIG. 3 shows the same substrate 200 after a PEALD deposition process isperformed to deposit an oxide layer 210. The narrow gaps 202 arecompletely filled, while the wide gap 204 is lined with oxide material210. The film 210 deposited on the bottom of the wide gap 204 may beslightly thicker than the film 210 deposited on the sidewalls of gap204. However, this thickness difference is much more pronounced in thenarrow gap 202 as it fills with material.

FIG. 4 shows a portion of substrate 200 at a time during the PEALDdeposition process. In particular, narrow gap 202 is shownmid-deposition. The deposited oxide layer 210 has a tapered profile,such that the film is thinner near the top of the gap and thicker nearthe bottom of the gap. This results in a diminishing gap that is smallerat the bottom than at the top. This shape is ideal for promotingvoid-free, seam-free fill. As material fills into the bottom of the gap,the mechanisms described above (e.g., preferential film densification,preferential ligand trapping, and/or crosslinking) may act to fill thefeature without any voids or seams. Experimental results demonstratingsuch a fill mechanism are included below in the Experimental section.

This fill mechanism has not been previously observed with PEALD typeprocesses. Instead, conventional PEALD processes form films that have nosuch tapered profile, where more vertical sidewalls grow towards oneanother and meet in the center. In these conventional methods, chemicalsmay get trapped in the extremely narrow void/seam formed in the centerof the gap. This trapping is likely to occur, in part because the entireheight of the gap closes in at substantially the same time. Conversely,with the disclosed methods, the sidewalls close in towards each other toa greater degree towards the bottom of the gap as opposed to the top ofthe gap. Thus, as the sidewalls grow towards one another, the bottom ofthe deposited film grows upwards, and chemicals present in the gap arepushed out. This results in a process where seam and void formation isavoided, producing an excellent quality filled gap.

In some embodiments, a gap filled by a PEALD operation has a reentrantprofile. In other words, the gap is smaller at an upper portion andwider at a lower portion. It has been observed that bottom-up fill canbe achieved with the disclosed PEALD process, even with gaps that have asomewhat reentrant profile. These results are shown below in theExperimental section.

Chamber Conditions

The PEALD process has been shown to be fairly resilient to changes intemperature. In particular, the process has been shown to be effectiveat 200° C. and 400° C. In some embodiments, therefore, the process isconducted at a temperature between about 200-400° C. In other cases,however, the temperature may fall outside this range.

The pressure inside the reaction chamber during the PEALD process may bebetween about 1-10 Torr, or between about 3-7 Torr, for example about 6Torr.

Plasma Generation Conditions

In the PEALD operation, the substrate is exposed to plasma to drive thereaction between the first and second reactants. Various types of plasmamay be used to drive this reaction including capacitively coupledplasmas and inductively coupled plasmas. Various types of plasmagenerators may be used including RF, DC, and microwave plasmagenerators. Moreover, according to various embodiments, the plasma maybe direct or remote.

The gas used to generate the plasma may include an inert gas such asargon or helium. The gas will also typically include one of thereactants, for example an oxidizing reactant where an oxide film isbeing formed.

In many cases, an RF signal is used to drive plasma formation. In someembodiments, the RF applied is high frequency RF only, for example at afrequency of about 13.56 or 27 MHz. In other embodiments, the RF has alow frequency component as well. The RF power delivered to drive plasmaformation may be between about 300 W and about 10 kW. In some cases, theRF power delivered is between about 4-6 kW, for example about 5 kW.These values represent the total power delivered, which is divided amongfour stations/pedestals.

Additional plasma generation conditions are discussed in U.S. patentapplication Ser. No. 13/084,399, filed Apr. 11, 2011, and titled “PLASMAACTIVATED CONFORMAL FILM DEPOSITION,” which is incorporated by referenceabove.

The duration of plasma exposure may vary between different embodiments.In some cases, RF power is applied for between about 10 milliseconds and3 seconds, or between about 0.25 seconds and about 1 second. In aparticular example, RF power is applied for about 0.5 seconds. The RFpower and RF time determine the RF flux delivered to the chamber. It hasbeen found that by increasing the RF flux (either by increasing RF timeor power), the wet etch rate (WER) of the film may be reduced. Becausethe PEALD process has shown a fair resilience to different RFconditions, these variables may be used to achieve a tunable WER.

Purge Conditions

Generally, two sweep/purge operations occur during a single cycle of aPEALD reaction. The first purge occurs after the dose of the firstreactant is delivered to the processing chamber, and may be referred toas a reactant purge. This purge is conducted to sweep out any remaining,non-adsorbed first reactant. The second purge occurs after the substrateis exposed to plasma, and may be referred to as the post-RF purge. Thispurge is conducted to sweep out any remaining reactants, as well as anyfilm formation byproducts.

There are various ways to purge a reaction chamber. One method involvessupplying the chamber with a flow of non-reactant gas (e.g., argon,helium, nitrogen, etc.) to sweep out any undesired species. With asweep, the pressure in the reaction chamber stays substantiallyconstant. Another method of purging a reaction chamber is to perform apump down. Where this is the case, a vacuum is applied and the reactionchamber is evacuated. During the evacuation, the pressure in thereaction chamber is significantly reduced, for example to less thanabout 1 Torr.

It has been found that gapfill results are better where the post-RFpurge includes a sweep, as compared to a pump down. Without wishing tobe bound by a particular theory or mechanism of action, it is believedthat the post-RF conditions, including the presence or absence of a pumpdown, may affect the surface functionality present on the surface of thedeposited film. This surface functionality may determine whether or notcrosslinking occurs between opposing sidewalls as the gap is filled. Oneway to encourage the desired bottom-up deposition pattern is to sweepthe reaction chamber instead of performing a pump down. Thus, in certainembodiments, no pump down is performed after plasma exposure during thePEALD deposition. In some cases, however, a pump down may be performedbetween a PEALD operation and a PECVD operation.

The reactant purge may be performed for a duration between about 0.1-1seconds, for example between about 0.2-0.5 seconds. In a particularexample, the reactant purge has a duration of about 0.3 seconds.

The post-RF purge may be performed for a duration between about 0.01-5seconds, for example between about 0.05-0.15 seconds. In one case thepost-RF purge has a duration of about 0.09 seconds.

Plasma Enhanced Chemical Vapor Deposition

The PECVD methods disclosed herein may be practiced after a PEALDprocess to finish filling gaps that were only partially filled/lined.This method is advantageous compared to a PEALD process alone because itoffers a much higher deposition rate, resulting in decreased processingtimes and increased throughput. Thus, the PEALD process may be used tofill small gaps and line large gaps, and then the PECVD process may beused to complete the filling of the large gaps. This offers a convenientway to fill features of varying sizes and aspect ratios. In many cases,the gaps can be filled without any intervening etching operations.

In a PECVD reaction, a substrate is exposed to one or more volatileprecursors, which react and/or decompose to produce the desired depositon the substrate surface. FIG. 5 shows a flow chart for a method 500 offilling a gap with PECVD. In various embodiments, the method 500 may beperformed after the method 100 of FIG. 1. The PECVD method generallybegins by flowing one or more reactants into the reaction chamber atoperation 501. The reactant delivery may continue as plasma is generatedin operation 503. The substrate surface is exposed to plasma, whichcauses deposition to occur on the substrate surface in operation 505.This process continues until a desired film thickness is reached. Atoperation 507, the plasma is extinguished and the reactant flow isterminated. Next, the reaction chamber is purged at operation 509.

In one example process, operation 501 includes flowing TEOS at a rate ofabout 1-20 mL/min and O₂ at a rate of about 2,000-30,000 sccm. RF poweris applied with an HF component between about 200-3,000 W, and an LFcomponent between about 200-2,500 W (divided among four stations). TheHF frequency is about 13.56 or 27 MHz, while the LF frequency is betweenabout 300-400 kHz. The pressure in the reaction chamber is between about1-10 Torr, and the temperature is between about 100-450° C. Of course,it is understood that in other embodiments, the reactants, chamberconditions, timing, etc. may vary depending on the desired film andapplication. The values provided in this section are not intended to belimiting.

PECVD methods and apparatus are further discussed and described in thefollowing patent documents, which are each herein incorporated byreference in their entireties: U.S. Pat. No. 7,381,644, titled “PULSEDPECVD METHOD FOR MODULATING HYDROGEN CONTENT IN HARD MASK”; U.S. Pat.No. 8,110,493, titled “PULSED PECVD METHOD FOR MODULATING HYDROGENCONTENT IN HARD MASK”; U.S. Pat. No. 7,923,376, titled “METHODS OFREDUCING DEFECTS IN PECVD TEOS FILMS”; and U.S. patent application Ser.No. 13/478,999, titled “PECVD DEPOSITION OF SMOOTH SILICON FILMS,” filedMay 23, 2012.

In many cases, there will be no downtime between a PEALD process and aPECVD process. For example, the PEALD process may end by extinguishingthe plasma, performing the post-RF purge (with or without a pump down),and then immediately flowing the PECVD reactant(s).

In some embodiments, hybrid PEALD/PECVD methods as discussed anddescribed in U.S. patent application Ser. No. 13/084,399, filed Apr. 11,2011, and titled “PLASMA ACTIVATED CONFORMAL FILM DEPOSITION,” which isincorporated by reference above, may be used.

PECVD Reactants

The PECVD reaction may be performed with either the same reactants asthe ALD reaction, or with different reactants. In one embodiment, thePEALD reaction is performed with BTBAS and a mixture of O₂/N₂O, and thePECVD reaction is performed with TEOS and/or silane. The TEOS and silanereactants have been found to be especially useful in practicing thePECVD reaction. Generally, the reactants listed above in the PEALDReactants section may be used in the PECVD reaction.

The flow rate of reactants may vary depending on the desired process. Inone embodiment related to PECVD undoped silicate glass (USG), SiH₄ isused as a reactant and has a flow rate between about 100-1,500 sccm,with a flow of N₂O between about 2,000-20,000 sccm. In anotherembodiment related to PECVD using TEOS, the flow of TEOS is betweenabout 1-20 mL/min, and the flow of O₂ is between about 2,000-30,000sccm.

Chamber Conditions

The temperature in the reaction chamber during the PECVD reaction may bebetween about 50-450° C., in certain embodiments. This range may beespecially appropriate for reactions using silane. Where other reactantsare used, the temperature range may be more limited or more broad, forexample between about 100-450° C. where TEOS is used.

The pressure in the reaction chamber during the PECVD reaction may bebetween about 1-10 Torr, for example about 5 Torr.

Because the chamber conditions are very similar between the PEALDoperation and the PECVD operation, it is feasible to implement bothtypes of reactions in a single reaction chamber. As discussed above,this is advantageous because it reduces or eliminates the risk ofmoisture entering the film as the substrate is moved between processingchambers, and reduces the need to perform a degassing operation betweenthe two processes.

Plasma Generation Conditions

The PECVD reactions are driven by exposure to plasma. The plasma may bea capacitively coupled plasma or a remotely generated inductivelycoupled plasma. For the reasons discussed above, it may be preferable toavoid using an in situ inductively coupled plasma.

The gas used to generate the plasma will include at least one reactant.The plasma generation gas may also include other species, as well. Forexample, in certain embodiments the plasma generation gas includes aninert gas.

The frequency used to drive plasma formation may contain both LF and HFcomponents. In some embodiments the HF frequency may be about 13.56 MHzor about 27 MHz. The LF frequency may be between about 300-400 kHz. TheHF RF power used to drive plasma formation may be between about200-3,000 W. The LF RF power used to drive plasma formation may bebetween about 200-2,500 W. These power levels represent the total powerdelivered, which is divided among four stations. The duration of plasmaexposure depends on the desired thickness of the deposited film.

In some embodiments, pulsed PECVD methods may be used. These methods mayinvolve pulsing precursor and/or RF power levels.

Purge Conditions

A purge is typically conducted after the PECVD deposition is complete.This purge operates to remove reactants and any byproducts from thereaction chamber. Because the film is already deposited at this point,the purge conditions are less important than with the PEALD reactions,which require many iterations of reactant purge and post-RF purge as thePEALD film is formed.

Apparatus

A suitable apparatus for performing the disclosed methods typicallyincludes hardware for accomplishing the process operations and a systemcontroller having instructions for controlling process operations inaccordance with the present invention. For example, in some embodiments,the hardware may include one or more PEALD, PECVD or joint PEALD/PECVDprocess stations included in a process tool.

FIG. 6 provides a block diagram of an example apparatus that may be usedto practice the disclosed embodiments. As shown, a reactor 600 includesa process chamber 624, which encloses other components of the reactorand serves to contain the plasma generated by, e.g., a capacitor typesystem including a showerhead 614 working in conjunction with a groundedheater block 620. A high-frequency RF generator 602, connected to amatching network 606, and a low-frequency RF generator 604 are connectedto showerhead 614. The power and frequency supplied by matching network606 is sufficient to generate a plasma from the process gas, for example400-700 W total energy. In one implementation of the present inventionboth the HFRF generator and the LFRF generator are used. In a typicalprocess, the high frequency RF component is generally between about 2-60MHz; in a preferred embodiment, the HF component is about 13.56 MHz or27 MHz. The low frequency LF component is generally between about250-400 kHz; in a particular embodiment, the LF component is about 350kHz.

Within the reactor, a wafer pedestal 618 supports a substrate 616. Thepedestal typically includes a chuck, a fork, or lift pins to hold andtransfer the substrate during and between the deposition and/or plasmatreatment reactions. The chuck may be an electrostatic chuck, amechanical chuck or various other types of chuck as are available foruse in the industry and/or research.

The process gases are introduced via inlet 612. Multiple source gaslines 610 are connected to manifold 608. The gases may be premixed ornot. Appropriate valving and mass flow control mechanisms are employedto ensure that the correct gases are delivered during the deposition andplasma treatment phases of the process. In the case that the chemicalprecursor(s) are delivered in liquid form, liquid flow controlmechanisms are employed. The liquid is then vaporized and mixed withother process gases during its transportation in a manifold heated aboveits vaporization point before reaching the deposition chamber.

Process gases exit chamber 600 via an outlet 622. A vacuum pump 626(e.g., a one or two stage mechanical dry pump and/or a turbomolecularpump) typically draws process gases out and maintains a suitably lowpressure within the reactor by a close loop controlled flow restrictiondevice, such as a throttle valve or a pendulum valve.

The invention may be implemented on a multi-station or single stationtool. In specific embodiments, the 300 mm Novellus Vector™ tool having a4-station deposition scheme or the 200 mm Sequel™ tool having a6-station deposition scheme are used. It is possible to index the wafersafter every deposition and/or post-deposition plasma anneal treatmentuntil all the required depositions and treatments are completed, ormultiple depositions and treatments can be conducted at a single stationbefore indexing the wafer. It has been shown that film stress is thesame in either case. However, conducting multiple depositions/treatmentson one station is substantially faster than indexing following eachdeposition and/or treatment.

FIG. 7 shows a schematic view of an embodiment of a multi-stationprocessing tool 2400 with an inbound load lock 2402 and an outbound loadlock 2404, either or both of which may comprise a remote plasma source.A robot 2406, at atmospheric pressure, is configured to move wafers froma cassette loaded through a pod 2408 into inbound load lock 2402 via anatmospheric port 2410. A wafer is placed by the robot 2406 on a pedestal2412 in the inbound load lock 2402, the atmospheric port 2410 is closed,and the load lock is pumped down. Where the inbound load lock 2402comprises a remote plasma source, the wafer may be exposed to a remoteplasma treatment in the load lock prior to being introduced into aprocessing chamber 2414. Further, the wafer also may be heated in theinbound load lock 2402 as well, for example, to remove moisture andadsorbed gases. Next, a chamber transport port 2416 to processingchamber 2414 is opened, and another robot (not shown) places the waferinto the reactor on a pedestal of a first station shown in the reactorfor processing. While the embodiment depicted in FIG. 4 includes loadlocks, it will be appreciated that, in some embodiments, direct entry ofa wafer into a process station may be provided.

The depicted processing chamber 2414 comprises four process stations,numbered from 1 to 4 in the embodiment shown in FIG. 4. Each station hasa heated pedestal (shown at 2418 for station 1), and gas line inlets. Itwill be appreciated that in some embodiments, each process station mayhave different or multiple purposes. For example, in some embodiments, aprocess station may be switchable between a PEALD and PECVD processmode. Additionally or alternatively, in some embodiments, processingchamber 2414 may include one or more matched pairs of PEALD and PECVDprocess stations. While the depicted processing chamber 2414 comprisesfour stations, it will be understood that a processing chamber accordingto the present disclosure may have any suitable number of stations. Forexample, in some embodiments, a processing chamber may have five or morestations, while in other embodiments a processing chamber may have threeor fewer stations.

FIG. 7 also depicts an embodiment of a wafer handling system 2490 fortransferring wafers within processing chamber 2414. In some embodiments,wafer handling system 2490 may transfer wafers between various processstations and/or between a process station and a load lock. It will beappreciated that any suitable wafer handling system may be employed.Non-limiting examples include wafer carousels and wafer handling robots.FIG. 7 also depicts an embodiment of a system controller 2450 employedto control process conditions and hardware states of process tool 2400.System controller 2450 may include one or more memory devices 2456, oneor more mass storage devices 2454, and one or more processors 2452.Processor 2452 may include a CPU or computer, analog and/or digitalinput/output connections, stepper motor controller boards, etc.

In some embodiments, system controller 2450 controls all of theactivities of process tool 2400. System controller 2450 executes systemcontrol software 2458 stored in mass storage device 2454, loaded intomemory device 2456, and executed on processor 2452. System controlsoftware 2458 may include instructions for controlling the timing,mixture of gases, chamber and/or station pressure, chamber and/orstation temperature, purge conditions and timing, wafer temperature, RFpower levels, RF frequencies, substrate, pedestal, chuck and/orsusceptor position, and other parameters of a particular processperformed by process tool 2400. System control software 2458 may beconfigured in any suitable way. For example, various process toolcomponent subroutines or control objects may be written to controloperation of the process tool components necessary to carry out variousprocess tool processes in accordance with the disclosed methods. Systemcontrol software 2458 may be coded in any suitable computer readableprogramming language.

In some embodiments, system control software 2458 may includeinput/output control (IOC) sequencing instructions for controlling thevarious parameters described above. For example, each phase of a PEALDprocess may include one or more instructions for execution by systemcontroller 2450. The instructions for setting process conditions for aPEALD process phase may be included in a corresponding PEALD recipephase. In some embodiments, the PEALD recipe phases may be sequentiallyarranged, so that all instructions for a PEALD process phase areexecuted concurrently with that process phase. The same can be said forPECVD processes and hybrid PEALD/PECVD processes.

Other computer software and/or programs stored on mass storage device2454 and/or memory device 2456 associated with system controller 2450may be employed in some embodiments. Examples of programs or sections ofprograms for this purpose include a substrate positioning program, aprocess gas control program, a pressure control program, a heatercontrol program, and a plasma control program.

A substrate positioning program may include program code for processtool components that are used to load the substrate onto pedestal 2418and to control the spacing between the substrate and other parts ofprocess tool 2400.

A process gas control program may include code for controlling gascomposition and flow rates and optionally for flowing gas into one ormore process stations prior to deposition in order to stabilize thepressure in the process station. A pressure control program may includecode for controlling the pressure in the process station by regulating,for example, a throttle valve in the exhaust system of the processstation, a gas flow into the process station, etc.

A heater control program may include code for controlling the current toa heating unit that is used to heat the substrate. Alternatively, theheater control program may control delivery of a heat transfer gas (suchas helium) to the substrate.

A plasma control program may include code for setting RF power levelsapplied to the process electrodes in one or more process stations.

In some embodiments, there may be a user interface associated withsystem controller 2450. The user interface may include a display screen,graphical software displays of the apparatus and/or process conditions,and user input devices such as pointing devices, keyboards, touchscreens, microphones, etc.

In some embodiments, parameters adjusted by system controller 2450 mayrelate to process conditions. Non-limiting examples include process gascomposition and flow rates, temperature, pressure, plasma conditions(such as RF bias power levels), pressure, temperature, etc. Theseparameters may be provided to the user in the form of a recipe, whichmay be entered utilizing the user interface.

Signals for monitoring the process may be provided by analog and/ordigital input connections of system controller 2450 from various processtool sensors. The signals for controlling the process may be output onthe analog and digital output connections of process tool 2400.Non-limiting examples of process tool sensors that may be monitoredinclude mass flow controllers, pressure sensors (such as manometers),thermocouples, etc. Appropriately programmed feedback and controlalgorithms may be used with data from these sensors to maintain processconditions.

System controller 2450 may provide program instructions for implementingthe above-described deposition processes. The program instructions maycontrol a variety of process parameters, such as DC power level, RFpower level, RF bias power level, pressure, temperature, etc. Theinstructions may control the parameters to operate in-situ deposition offilm stacks according to various embodiments described herein.

Lithographic patterning of a film typically comprises some or all of thefollowing steps, each step enabled with a number of possible tools: (1)application of photoresist on a workpiece, e.g., a substrate having asilicon nitride film formed thereon, using a spin-on or spray-on tool;(2) curing of photoresist using a hot plate or furnace or other suitablecuring tool; (3) exposing the photoresist to visible or UV or x-raylight with a tool such as a wafer stepper; (4) developing the resist soas to selectively remove resist and thereby pattern it using a tool suchas a wet bench or a spray developer; (5) transferring the resist patterninto an underlying film or workpiece by using a dry or plasma-assistedetching tool; and (6) removing the resist using a tool such as an RF ormicrowave plasma resist stripper. In some embodiments, an ashable hardmask layer (such as an amorphous carbon layer) and another suitable hardmask (such as an antireflective layer) may be deposited prior toapplying the photoresist.

It is to be understood that the configurations and/or approachesdescribed herein are exemplary in nature, and that these specificembodiments or examples are not to be considered in a limiting sense,because numerous variations are possible. The specific routines ormethods described herein may represent one or more of any number ofprocessing strategies. As such, various acts illustrated may beperformed in the sequence illustrated, in other sequences, in parallel,or in some cases omitted. Likewise, the order of the above describedprocesses may be changed.

The subject matter of the present disclosure includes all novel andnonobvious combinations and sub-combinations of the various processes,systems and configurations, and other features, functions, acts, and/orproperties disclosed herein, as well as any and all equivalents thereof.

EXPERIMENTAL

FIG. 8 presents a gap 802 partially filled with silicon oxide film 804in a PEALD process according to the disclosed methods. Markers 806 areprovided in order to evaluate the conformality of the oxide film 804.For the sake of clarity, only one marker is labeled in FIG. 8. Each ofthe markers 806 has an identical height. Thus, it is apparent that thedeposited film is thicker at the bottom than at the top. Further, thelower sidewalls are thicker than the upper sidewalls, which are boththicker than the top region. The film thickness near the top is aboutthe same as the film thickness in the top corner. The silicon oxide film804 was deposited at about 400° C., with a 2 mL/min flow of BTBAS for aduration of about 0.3 seconds, followed by a reactant purge with a sweepduration of about 0.3 seconds, followed by delivery of a mixture ofO₂/N₂O at 10 SLM each, coincident with a 0.5 second exposure to RFplasma, followed by a post-RF purge having a duration of 0.09 seconds.The plasma was a high frequency plasma, with a power of about 5 kW splitamong four pedestals. The film 804 shows a tapered profile, which isideal for filling gaps, especially those having large aspect ratios.Although the PEALD process used to create the film 804 was terminatedbefore the gap 802 was completely filled (in order to view the fillbehavior), the PEALD process can be continued to completely fill the gap802 without formation of any seams or voids.

FIG. 9 shows a substrate with a number of gaps filled with silicon-oxideaccording to the disclosed PEALD methods. The gaps in this case have anaspect ratio of about 7:1, and a CD on the order of about 30 nm. Thedeposited film was dense, and did not show any seams or voids.

FIG. 10 shows a close-up view of a gap filled according to the disclosedPEALD methods. No seams or voids are detected in the fill.

FIG. 11 shows a substrate having high aspect ratio gaps (AR about 8:1)filled according to the disclosed PEALD methods. Notably, the gap on theright shows some degree of reentrancy. The markers A and B are the samelength. It can be seen that the gap is wider at marker B than at markerA. While the width difference is fairly slight, even small degrees ofreentrancy will result in the formation of voids under many conventionalmethods.

It should be noted that the gaps shown in FIGS. 8-11 were filled with noetching operations performed.

FIG. 12 shows a wide gap filled with silicon oxide according to adisclosed PECVD method with TEOS performed at about 200° C. The filmdeposited was about 2,000 Å thick, and showed good gap fill properties,with no voids or seams. No etching operations were performed.

What is claimed is:
 1. A method of filling a gap adjacent to a fieldregion on a substrate surface, the method comprising: (a) introducing afirst reactant in vapor phase into a reaction chamber having thesubstrate therein, and allowing the first reactant to adsorb onto thesubstrate surface; (b) introducing a second reactant in vapor phase intothe reaction chamber; (c) exposing the substrate surface to plasma todrive a surface reaction between the first and second reactants on thesubstrate surface to form a film layer that lines the bottom andsidewalls of the gap, wherein the film layer is denser near the fieldregion and upper sidewalls of the gap compared to near the bottom andlower sidewalls of the gap; (d) sweeping the reaction chamber withoutperforming a pumpdown; and (e) repeating operations (a) through (d) toform additional film layers to thereby fill the gap through a bottom-upfill mechanism, without formation of a void or seam.
 2. The method ofclaim 1, wherein the first reactant comprises a silicon-containingreactant and the second reactant comprises an oxidizing reactant.
 3. Themethod of claim 1, wherein the gap is reentrant.
 4. The method of claim1, wherein the gap is filled through a bottom-up fill mechanism in whichthe film layers are deposited thinner near the top of the gap andthicker near the bottom of the gap.